When Do Most Miscarriages Happen?
Most miscarriages occur during the first trimester of pregnancy, with approximately 80% happening within the first 12 weeks of gestation. 1
Timing of Miscarriages
- The majority of pregnancy losses (about 80%) occur during the first 12 weeks of pregnancy, which is the first trimester 1
- Spontaneous expulsion of the blastocyst from the uterine cavity accounts for approximately 15-20% of recognized pregnancies 2
- Early miscarriages (occurring during the first 14 weeks) are much more common than late miscarriages (after 14 weeks) 3
Risk Factors and Causes of Miscarriage
Genetic Factors
- More than half of early pregnancy losses result from genetic defects, usually presenting as abnormal chromosome numbers or gene rearrangements in the embryo 1
- Recent research has identified specific gene mutations that may be implicated in both sporadic and recurrent miscarriages 1
Maternal Age
- Advanced maternal age is independently associated with increased risk of miscarriage 4
- Women aged 35 years or older have a significantly higher risk of miscarriage (OR 1.85; 95% CI, 1.35-2.52) compared to younger women 5
Diminished Ovarian Reserve
- Low serum Anti-Müllerian Hormone (AMH) levels (<0.7 ng/ml) are associated with a significantly higher risk of miscarriage (OR 1.91; 95% CI, 1.40-2.60) 5
- For women over 35 years old with diminished ovarian reserve, the risk is even higher (OR 2.05; 95% CI, 1.42-2.95) 5
Infections
- Potentially preventable infections may account for up to 15% of early miscarriages and up to 66% of late miscarriages 6
- Systemic infections associated with increased miscarriage risk include malaria, brucellosis, cytomegalovirus, HIV, dengue fever, and influenza 6
- Bacterial vaginosis has also been linked to increased risk of pregnancy loss 6
Other Risk Factors
- Previous miscarriage, termination, and infertility 4
- Assisted conception methods 4
- Low pre-pregnancy body mass index 4
- Regular or high alcohol consumption 4
- High stress levels, including exposure to stressful or traumatic events 4
- High paternal age and changing partners 4
Protective Factors
- Previous live birth 4
- Nausea during pregnancy 4
- Vitamin supplementation 4
- Daily consumption of fresh fruits and vegetables 4
Clinical Presentation
- The earliest sign of miscarriage is typically bleeding or spotting 2
- Pain often accompanies the bleeding 2
- Diagnosis is made through patient history, physical examination, ultrasound, and hCG level testing 2
Management Considerations
- Early miscarriages can be managed expectantly, medically, or surgically 3
- Surgical methods (such as suction aspiration) are generally more effective than medical methods (such as misoprostol), which in turn are more effective than expectant management 3
- Surgery during pregnancy carries a slightly higher risk of miscarriage during the first trimester 5
Important Considerations for Healthcare Providers
- Healthcare providers have an obligation to inform women of their rights after pregnancy loss 2
- Psychological support is an important aspect of care for women experiencing miscarriage 2
- Miscarriage should be recognized as an interdisciplinary issue involving obstetrics, epidemiology, public health, psychology, and other specialties 2